1. Field of the Invention
The invention is based on a method for the bubble-free joining of a semiconductor component to a component part serving as substrate according to the generic type.
2. Discussion of the Background
In the technology of power electronics, the semiconductor components, which can have considerable cross-sectional areas, must be placed in contact, that is to say joined with circuit continuity, with a substrate used for supplying the current.
This can be achieved in various ways:
(a) Bonding with a one- or two-component epoxy resin based conductive adhesive.
(b) Joining the component to the substrate by coating the latter with liquid solder and placing the former in floating manner onto the solder.
(c) Soldering with gold under pressure in a vacuum.
(d) Purely mechanical pressure contact: the component parts which are provided with plans metallic surfaces and pressed together under pressure are built into a case.
The conventional technologies lead to the following partially unsatisfactory results and inadequacies, particularly in the case of large-area components:
(i) Poor heat dissipation and non-uniform current distribution due to gas inclusions.
(ii) Uncontrollable thickness of the solder layer and non-uniform coating due to oxides and dust particles.
(iii) High material costs and risk of the formation of voids.
(iv) High material costs, expensive and elaborate construction methods.
In soldering methods similar to (b), the impurities can be squeezed outward by applying weights and using soldering gauges, but the soldering gap remains largely undefined and wedge errors occur.
The various soldering techniques are known from, among others, the following publications:
H. Parthey, "Boundary-Layer Problems during Soldering", Mitteilungen Forschungsgesellschaft Blechverarbeitung, 1965, No. 23/24, pages 365-367.
W. Leibfried, "Soldering of Chip Components", DVS Report, Volume 82, Munich 1983.
H. J. Hartmann, "Development of Reliable Contacting Methods using Soft Solders for Electronic Circuits, including Investigation of the Interface Reactions during Soft Soldering", Research Report of BMFT-FB T79-164. December 1979.
A need exists therefore for improving the conventional joining technologies to make them more reliable.